I had both NHS and private NT scan the private hosp where i went does the quad test which is 93%accurate compared to the NHS which is 70% accurate.For me this was just a bit extra piece of mind, they also take the nasal bone into consideration My risk on the NHS was 1:2016 with my private scan it was 1:20,000 and with the nasal bone 1:50,000 and was deemed negative. If you are looking at a private scan make sure it's one that does the quad test.